This disclosure relates generally to test equipment for nondestructive evaluation systems, and more specifically to wet-coupled ultrasonic evaluation systems for the inspection of parts.
As new materials, such as composite materials, are used in more applications throughout the aircraft industry and other industries, the use of nondestructive test equipment, such as ultrasonic test equipment, to inspect fabricated parts prior to use has become widespread. Ultrasonic test equipment allows an operator to nondestructively inspect the interior of parts, such as fuselage or wing components, for areas of discontinuity such as structural inconsistencies, imperfections, delaminations, foreign objects introduced during fabrication, etc.
Ultrasonic test equipment utilizes a high frequency sound wave generated by an ultrasonic transducer, sometimes referred to as a probe, that is located near the surface of the part being tested. The ultrasonic transducer is oriented such that the high frequency sound wave travels through the part, usually in the height or thickness direction. When the sound wave encounters a discontinuity, such as a delamination, or a change in the stiffness of the material, part of the sound energy is reflected. The reflected sound energy travels back through the part and is received by the same ultrasonic transducer, which acts as both a transmitter and receiver in what is commonly referred to as a “pulse echo” ultrasonic test system. Alternatively, the high frequency sound wave generated by the ultrasonic transmitter passes through the entire thickness of the part and is received on the opposite side of the part by a separate receiver in what is commonly known as “through transmission” ultrasonic testing. Pulse echo ultrasonic testing is the most common technique in use because access to only one side of a part is required.
The waveform of the received RF signal from an ultrasonic test is recorded by the test equipment and/or displayed on a monitor or other display device. The data contained in the RF signal can be displayed in a number of different formats for review by technicians. Any distortion in received signals can be an impediment to effective use of the test system to identify potential unwanted discontinuities in the part being tested. Distortion and/or interference in the received signals is particularly problematic when it leads an operator or technician to falsely believe that a discontinuity is present.
The production of a large variety of relatively small, low volume parts produces an extra set of challenges for nondestructive inspection. Conventionally, custom designed part holders unique to each part that is to be inspected are utilized. Such customized part holders may typically support the ends of the part, leaving the center free from obstruction, such that only a very small portion of the part will be in actual contact with the fixture. Such customized part holders are undesirable, however, when many different parts are being ultrasonically scanned for inspection purposes. For example, in an aircraft assembly, as many as 80 different structural parts of varying shape and size are assembled to define a portion of an aircraft. Preferably, each of the 80 structural parts needs to be scanned and inspected to ensure the structural integrity thereof. Creating a specialized part holder for each of the 80 parts would be costly, time consuming, and generally impractical for the relatively low volume of parts involved to produce a limited number of aircraft.
It would be desirable to form a more universally usable part holder for ultrasonic testing that may be reliably used with a variety of parts without adversely affecting the test results.